Lethal Dose 50% (College Board AP® Environmental Science): Flashcards
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Define lethal dose 50% (LD₅₀).
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Define lethal dose 50% (LD₅₀).
Lethal dose 50% (LD₅₀) is the amount of a material that causes the death of 50% (half) of a population.
True or False?
LD₅₀ is used to measure the long-term toxicity of a substance.
False.
LD₅₀ measures the short-term toxicity of a substance.
What does "LC" stand for in LC₅₀?
In LC₅₀, LC stands for lethal concentration.
How is the material given when measuring LD₅₀?
For LD₅₀, the material is given all at once as one dose.
The LD₅₀ of a toxic substance refers to a dose that has been .
The LD₅₀ of a toxic substance refers to a dose that has been ingested.
What does an LC₅₀ value relate to?
An LC₅₀ value relates to the chemical concentration in water or air that kills 50% of test animals in a specific time period.
True or False?
An LD₅₀ value applies equally to every species exposed to the substance.
False.
An LD₅₀ value refers to the population of a particular species, so it is specific to the species tested.
What exposure periods are used for LC₅₀ in air and in water?
LC₅₀ is measured after 4 hours of exposure for inhalation and 96 hours of exposure in water.
Define dose-response curve.
A dose-response curve is a graph showing how the magnitude of a subject's response to a substance, such as a drug or toxin, changes with the dose.
The response shown on a dose-response curve can be either therapeutic or .
The response shown on a dose-response curve can be either therapeutic or toxic.
True or False?
A dose-response curve plots the response against the time that has passed.
False.
The response (y-axis) is plotted against the dose or concentration of the substance (x-axis), not time.
What shape is a typical dose-response curve?
A typical dose-response curve is sigmoidal, with plateaus at the top and bottom.
Define threshold (on a dose-response curve).
The threshold is the lowest dose at which a reaction can be seen.
On a dose-response curve, a steep means that even small changes in dose can cause big changes in response.
On a dose-response curve, a steep slope means that even small changes in dose can cause big changes in response.
Define plateau (on a dose-response curve).
The plateau is the point of maximum response, where the response does not change even when the dose is increased.
What is the ceiling effect?
The ceiling effect is the point at which increasing the dose no longer increases the drug's effect and may even cause harm.
What does a dose-response curve help to find when a new drug is tested?
A dose-response curve helps to find the drug's effective dose range.
How do dose-response studies help to set safety standards for chemical exposure in industry?
Dose-response studies help to determine threshold limit values and acceptable exposure levels for employees, so that chemical exposure stays below dangerous levels.
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